In order to improve the surface hardness and wear resistance of rectangular pipe, it can be processed some of the surface, ie the surface of pure flame of fire, high, intermediate frequency surface hardening and some chemical treatment and the like. Generally high, intermediate frequency surface hardening of the majority, it is heated at a temperature of 850-950 ℃. Given its poor thermal conductivity, so the heating speed is not too fast, otherwise it will melt with some defects quenching cracks. Induction hardening requirements Rectangular Pipe normalizing matrix organization is mainly pearlite. The cooling spray water or an aqueous solution of polyvinyl alcohol, tempering temperature in the range of 200-400 ℃, hardness 40-50HRC, hardness and wear resistance to ensure Rectangular Pipe surface.

Rectangular pipe heat treatment also has the following three advantages:

(A) High dimensional stability for precision rectangular pipe, which requires high precision, it must maintain dimensional stability, as a result school straight in the air, the cooling rate is slow, so the role of austenite has stabilized will increase the amount of retained austenite tissue rectangular pipe, it must be cold treatment;

(B) Reduce quenching distortion due to the elongated square and rectangular tube, so hardened process easily deformed, it must be strictly controlled deformation, heat treatment is crucial step in the quenching process, the use of plastic be supercooled austenite timely alignment, which is a key step to ensure their conformity rate, for which should be hot bath quenching or cooling heat straightening proposed some time while heating should be hung upon heating, to reduce the deformation hardening in oil, for high-precision guide rail, to reduce the deformation of the gas nitriding or plasma nitriding, etc;

(C) High hardness main square and rectangular tube withstand contact fatigue loads, it must have a high hardness, and therefore should be hardening, or hardening or chemical heat treatment, followed by tempering process.